The present invention relates to a color image forming apparatus in which a color image is formed on a photoreceptor belt by means of electrophotography and the formed color image is transferred onto a transfer sheet.
A conventional color image forming apparatus in which a photoreceptor belt is provided approximately horizontally and a plurality of developing units are disposed below the lower surface of the photoreceptor belt, is disclosed, for example, by the Japanese Patent Application Open to Public Inspection No. 151560/1986. The color image forming apparatus in the prior art is widely known. According to the color image forming apparatus, the photoreceptor belt is disposed approximately horizontally, and a plurality of developing units are disposed in parallel below the lower surface of the photoreceptor belt while the openings of the developing units are directed upward. There are provided two rotating rollers which are opposed to each other, and the photoreceptor belt is wrapped around the rollers. Around the photoreceptor belt, there are provided; a charger; an exposure unit of a laser writing system; developing units which accommodates developers of yellow, magenta, cyan and black; a transfer unit which is disposed in such a manner that the transfer unit faces a curved portion of the photoreceptor belt wrapped around one rotating roller, wherein a predetermined gap is formed between the transfer unit and the photoreceptor belt; and a fixing unit disposed in an upper location of the transfer unit. Further, there is provided a cleaning unit which is disposed in such a manner that the cleaning unit faces a curved portion of the photoreceptor belt wrapped around the other rotating roller, wherein a predetermined gap is formed between the cleaning unit and the photoreceptor belt.
The color image forming apparatus with this arrangement consecutively records color images on recording papers which are conveyed intermittently.
In a practical color printer or a color copier, color toner remaining on the surface of a photoreceptor belt is removed with a cleaning unit. After a number of cleaning operations, the charger disposed adjacent to the cleaning unit and the surfaces of a lens and a mirror of the laser writing unit become stained with scattered toner, so that the quality of toner images formed the surface of a photoreceptor belt or a recording paper is affected by the scattered toner.
In the case of a color image forming apparatus in which the charger and the transfer unit are disposed at different end portions of the photoreceptor belt with regard to its longitudinal direction, the dimensions of the image forming apparatus are necessarily increased.